Analyze Jenkins payloads

Summary:
Commit 827b3ab83659 introduced a schema for Jenkins configuration.

This change implements the analyzer code for this configuration.

Ref T953.

Test Plan: Unit tests based on GitHub webhooks analyser code.

Reviewers: dereckson

Subscribers: alken-orin, dereckson

Maniphest Tasks: T953

Differential Revision: https://devcentral.nasqueron.org/D626